1. Field of the Invention
This invention relates to a tip tool guide apparatus, and a method for bringing in the tip tool guide apparatus.
The tip tool guide apparatus of the present invention is an apparatus which is brought into a water chamber of a steam generator of nuclear power equipment, and guides various tip tools, necessary to perform shot peening, along a necessary processing region.
The method for bringing in the tip tool guide apparatus according to the present invention is a method for efficiently bringing the tip tools into and out of the water chamber of the steam generator of nuclear power equipment via a manhole formed in the water chamber.
2. Description of the Related Art
FIG. 39 shows a primary system of pressurized light water reactor nuclear power equipment. As shown in this drawing, a reactor vessel 1, a pressurizer 2, a steam generator 3, and a pump 4 are sequentially connected by a main coolant pipe 5 to form a primary circulating path. In this primary circulating path, a main coolant (primary water) 6 pressure-fed by the pump 4 flows in a circulating manner.
The primary water 6 at a high temperature and a high pressure, which has been heated in the reactor vessel 1, is supplied to the steam generator 3 through the main coolant pipe 5 while being maintained at a constant pressure by the pressurizer 2. This primary water 6 enters an inlet-side water chamber 3b from an inlet pipe nozzle stub 3a of the steam generator 3, further flows through many inverted-U-shaped heat transfer tubes 3c, enters an outlet-side water chamber 3d, and exits from an outlet pipe nozzle stub 3e. 
On this occasion, secondary water 10 returned from a turbine is heated and evaporated by a group of the heat transfer tubes 3c, within which the high temperature primary water 6 flows. Steam 11 thus generated is separated upon steam-water separation by a steam separator 12, and supplied to the turbine (not shown) to drive the turbine. This driving of the turbine rotationally drives a generator (not shown) to generate electric power.
A lower portion of the steam generator 3 is shown enlarged in FIG. 40. As shown in FIG. 40, the inlet-side water chamber 3b and the outlet-side water chamber 3d are separated from each other by a partition plate 3f. The inlet pipe nozzle stub 3a is installed in a downwardly inclined posture when viewed from the inlet-side water chamber 3b, while the outlet pipe nozzle stub 3e is installed in a downwardly inclined posture when viewed from the outlet-side water chamber 3d. 
FIG. 41 shows a welded joint structure for welding between the nozzle stub 3e (3a) and the main coolant pipe 5. The nozzle stub 3e (3a) is formed from a material which is carbon steel or low alloy steel. The interior of the nozzle stub 3e (3a) has been subjected to build-up welding with stainless steel 30, and a buttering portion 31 of a nickel-chromium-iron alloy (600-alloy) is applied to an end portion of the nozzle stub 3e (3a).
A safe end 32 formed from stainless steel is welded to the buttering portion 31 with the use of a weld zone 33 of 600-alloy. The main coolant pipe 5 is welded to the other end of the safe end 32 with the use of a welding material 34 of stainless steel.
The 600-alloy material, as a nickel-chromium-iron alloy, in the pressurized light water reactor nuclear power equipment may undergo stress-corrosion cracking as the equipment is very aged, if high stress occurs in the presence of primary water at a high temperature.
Residual stress has been generated in the 600-alloy buttering portion 31 and the 600-alloy weld zone 33 because of welding during manufacture. To suppress the stress-corrosion cracking of the 600-alloy buttering portion 31 and the 600-alloy weld zone 33 contacting the primary water, it is effective to decrease the residual stress generated in the 600-alloy buttering portion 31 and the 600-alloy weld zone 33.
In the existing nuclear power equipment, therefore, it has been considered an effective method to withdraw the main coolant (primary water) 6, and perform shot peening of the surfaces of the 600-alloy buttering portion 31 and the 600-alloy weld zone 33 (their inner peripheral surfaces) from the inner peripheral surface side of the nozzle stubs 3a, 3e, thereby decreasing the residual stress of this region. FIG. 42 shows a peening width W of a processing region which is subjected to shot peening. Japanese Unexamined Patent Publication No. 2004-169100 is available as a document showing an earlier technology.
However, the shot peening performed from the inner peripheral surface side of the inlet pipe nozzle stub 3a and the outlet pipe nozzle stub 3e posed the following problems:
(1) With the existing nuclear power equipment, the dose rates within the water chambers 3b and 3d are extremely high. To ensure safety, therefore, the time for which an operator stays within the water chamber 3b or 3d needs to be limited to a minimum required time.(2) As shown in FIG. 43 which is a sectional view taken along line X-X in FIG. 40, a manhole H of a small diameter (about 400 mm) is formed in the outlet-side water chamber 3d. Similarly, a manhole H of a small diameter is formed in the inlet-side water chamber 3b. To enter the water chamber 3b or 3d and apply shot peening to the inner peripheral surface of the nozzle stub 3a or 3e, this narrow manhole H is the only passage leading to the water chamber 3b or 3d. 
Thus, an apparatus brought into the water chamber 3b or 3d for the shot peening operation needs to be a compact and lightweight one of a shape allowing passage through the manhole H.
The apparatus also needs to be contrived such that it can be easily brought into the water chamber 3b or 3d. 
(3) It is also necessary that the shot peening operation can be performed accurately and promptly.
It is true that if shot peening of the inlet pipe nozzle stub 3a and the outlet pipe nozzle stub 3e can be performed from the inner peripheral surface side thereof, the stress-corrosion cracking of the 600-alloy buttering portion 31 and the 600-alloy weld zone 33 can be suppressed. However, there has been no concrete instrument which can apply shot peening accurately and promptly while solving the above-mentioned problems.